Dielectric Properties and Kinetic Study on the Degradation of Bismaleimide Resin

摘要

Bismaleimide, a thermosetting resin, is attracting interest in the aerospace industry due to its epoxy-like processability, but better high-temperature performance than epoxy. As this industry shifts towards using higher overall percentages of fiber-reinforced polymer-matrix composites, understanding how these systems degrade, in particular the polymer matrix component, becomes increasingly important. Additionally, these materials are now being exposed to a wider variety of environmental and physical conditions, as new areas of usage, for both primary and secondary roles, are being explored. In this context, the thermo- oxidative degradation kinetics of bismaleimide are explored. Two model-free isoconversional methods, the Friedman and Ozawa-Flynn-Wall methods, are used to analyze results from thermogravimetric analysis at a variety of heating rates (5, 10, 20, and 50 ° C/min) from room temperature to 800 ° C. From these methods, the activation energies associated with particular degradation steps have been determined. Additionally, the dielectric properties of the bismaleimide resin were measured as a function of frequency (0.10 Hz to 1MHz) and temperature (-140 ° C to 160 ° C) using spectroscopic techniques. One primary dielectric relaxation (gamma) was observed in the temperature and frequency ranges used and modeled using a Havriliak-Negami model. The associated activation energy of the relaxation was calculated to be 41.31 kJ/mol.